soSIMPLE Calendar Plugin is licensed per end-user organization.
Within each organization you can use the soSIMPLE Calendar Add-On for an unlimited number of users and for an unlimited number of calendars in your custom app.
The standard license limits you to install and register the Add-on in three files and three hosts within your organization. This allows you to have multiple-file solutions or multiple test installations for development.
If you develop custom apps for multiple clients, you must either buy a standard license for each client, or you may consider a developer license.